Five people stand along a street waiting for a bus to arrive. The street is 9 yards

Question:

Five people stand along a street waiting for a bus to arrive. The street is 9 yards away from a building. The distance (in yards) of each person from the street has density fX(x) = √x/18, for 0 ≤ x ≤ 9. These distances are independent. Find the density of the greatest of the five distances from the street.